The UFC constantly reminds all their fighters to be model employees...and enforces it by suspending and/or terminating a fighter when $#!% happens...but they aren't as consistent with enforcement as the fighters are with making mistakes...and i do suspect that it is dependent on whether a particular fighter is a big ticket-seller or not...

nick diaz gets suspended for a year for smoking prescribed weed 8 days before a fight, but chael sonnen gets a pass for his prescribed test shots...